Many endoscopes view only directly forward. Others feature fixed or movable reflectors in the distal portion to allow off-axis viewing. Some, most commonly flexible types, feature actuated bending portions at the distal end. This invention is applicable to all types of axial, non-axial, and variable direction of view endoscopes.
Today, typically a camera means, such as a CCD or CMOS chip, is attached to the endoscope. It receives the image from the image forwarding system in the endoscope and produces a signal for a screen to display the endoscopic image. The surgeon observes this screen while manipulating the endoscope. A surgical or diagnostic procedure generally requires the surgeon to pitch the endoscope about a lateral axis or roll it about a longitudinal axis. As these manipulations occur to an endoscope with an attached camera, the camera faithfully relates what it sees, with its own upright axis displayed as the upright axis of the image on the display. This often results in rotation of the viewed image.
This is the very problem. When the image is displayed on the screen and the endoscope is manipulated, it is as though the surgeon must tilt his head to follow the rotating image. However, the surgeon is standing up, and the rotating image can be confusing to him. What he really wants to see on the screen is an image that is oriented the same as he would see it if he were inside the examination site, standing up, with the same upright orientation.
A solution to this problem is proposed in U.S. Pat. No. 5,307,804 to Bonnet (1994), which is incorporated herein by reference in its entirety. An object of this invention was to maintain the orientation of an endoscopic image without the use of electronic sensing and positioning devices. A pendulum fixed to a camera is rotatably attached to an endoscope. The pendulum maintains an orientation with respect to gravity around the endoscope longitudinal axis. As the endoscope rotates, the pendulum causes the camera to rotate in the opposite direction relative to the endoscope. This is intended to maintain the image in a proper orientation.
An endoscope with rotational orientation correction is also suggested in U.S. Pat. No. 5,899,851 to Koninckx (1999), which is incorporated herein by reference in its entirety. An electronic rotation pick-up means responsive to gravity senses rotation of a camera around the endoscope longitudinal axis. An image rotator rotates the camera image according to the rotation signal from the rotation pick-up means.
Another endoscope and camera system with rotational orientation correction is disclosed in U.S. Pat. No. 6,097,423 to Mattsson-Boze, et al. (2000), which is incorporated herein by reference in its entirety. Electronic sensing and positioning devices combine to sense and correct the rotation of a camera rotatably attached to an endoscope. An accelerometer fixed to the camera serves as an electronic rotation pick-up means responsive to gravity. A motor rotates the camera according to signals from the accelerometer. This accelerometer and motor system is functionally equivalent to the pendulum described by Bonnet. While the pendulum relies on the force of gravity to rotate, the small accelerometer sensitively measures gravity and the motor rotates the assembly accordingly. The system can therefore be thought of as an electro mechanical pendulum. Mattsson-Boze also recognizes rotation of the image by electronic manipulation to correct the image orientation, but actively discourages this practice for several reasons.
U.S. Pat. No. 6,471,637 to Green, et al. (2002), which is incorporated herein by reference in its entirety, discloses the same apparatus as disclosed in Mattsson-Boze, and suggests two alternative methods for image rotation. In the first method, an optical image rotator is used instead of a rotating camera. In the second method, electronic manipulation is used to correct the image orientation. Also, one or more gyroscopes are suggested as alternative electronic rotation pick-up means.
U.S. patent application Ser. No. 10/093,650 by Chatenever, et al. (2002), which is incorporated herein by reference in its entirety, discloses the same apparatus as disclosed in Mattsson-Boze and in Green, and suggests two alternative methods for electronic rotation pick-up. In the first method, image analysis is used to compute a rotational signal. In the second method, a machine vision system is used to compute a rotation signal.
All of the above solutions compensate only for roll about the longitudinal axis and provide a rotationally corrected image for axial viewing endoscopes. They also provide an approximation of the correct orientation for slightly oblique viewing endoscopes held near horizontal. None of the above disclosures suggest a solution that works for significantly oblique, side, or retro viewing endoscopes.
Oblique, side, or retro viewing endoscopes require a solution that takes into account the off-axis viewing direction. Variable direction-of-view endoscopes further complicate the situation. In response to this need, U.S. patent application Ser. No. 10/754,130 by Schara, et al. discloses a method which provides a general solution applicable for all angles of pitch and roll, and for all endoscopic viewing angles.
While comprehensive, this solution relies on mathematical parameterizations and computations taking into account endoscope pitch, roll, and viewing angle to obtain the required amount of rotational image compensation. It would be desirable to obtain a direct solution to the image leveling problem for off-axis and variable direction of view endoscopes without the need for computations requiring information about the endoscope attitude and viewing angle.
Accordingly, it is an object of this invention to provide a means for maintaining the proper upright orientation (with respect to the viewer) of a viewed image from an off-axis or variable direction of view endoscope without the need for complicated computations.